The Third Generation Partnership Project (3GPP) has examined the standardization of the MTC. The MTC is also called a Machine-to-Machine (M2M) network or a sensor network. The 3GPP defines mobile stations (MSs, USs) implemented in machines and sensors for the MTC as “MTC devices”. The MTC devices are typically arranged in various types of equipment including machines (e.g., vending machines, gas meters, electric meters, vehicles, railway vehicles) and sensors (e.g., environmental, agricultural, or traffic sensors). The MTC devices are connected to a Public Land Mobile Network (PLMN) and communicate with an MTC application server (AS). The MTC application server is arranged outside the PLMN (external network), executes an MTC application, and communicates with MTC UE applications implemented in the MTC devices. The MTC application server is typically controlled by an MTC service provider (M2M service provider).
The 3GPP specifies network elements including a Service Capability Server (SCS) and a Machine Type Communication Inter Working Function (MTC-IWF), reference points, and procedures to allow the MTC application server to communicate with the MTC devices (see Non-patent literature 1). The reference points are also called as “interfaces”.
The SCS is an entity to connect the MTC application server to the 3GPP PLMN and to allow the MTC application server to communicate with a UE (i.e., MTC device) through a PLMN service defined by the 3GPP. Further, the SCS allows the MTC application server to communicate with the MTC-IWF. The SCS is assumed to be controlled by an operator of the PLMN or the MTC service provider.
The MTC-IWF is a control-plane entity that belongs to the PLMN. The MTC-IWF has a signaling interface (reference point) with the SCS and has connections with nodes in the PLMN (e.g., Home Subscriber Server (HSS), a Short Message Service-Service Center (SMS-SC), a Serving GPRS Support Node (SGSN), a Mobility Management Entity (MME), and a Mobile Switching Center (MSC)). The MTC-IWF serves as a control-plane interface to allow the 3GPP PLMN and the M2M service layer including the SCS to cooperate (interwork) with each other while hiding the details of the topology of the 3GPP PLMN.